Significant Café au Lait Spot Size in Children
In prepubertal children, six or more café au lait macules measuring ≥0.5 cm (5 mm) in diameter are considered significant and meet one of the diagnostic criteria for neurofibromatosis type 1 (NF1). 1, 2
Size Thresholds by Age
- Prepubertal children: ≥0.5 cm (5 mm) diameter is the threshold when six or more spots are present 1, 2
- Postpubertal individuals: ≥1.5 cm (15 mm) diameter is the threshold when six or more spots are present 1, 2
- Single isolated spots: One or two café au lait macules of any size in an otherwise healthy child are generally not significant and are common, occurring in up to 25% of preschool-aged children 3, 4
Critical Number Threshold
The number "six or more" is the key diagnostic criterion, not just the size alone. 1, 2 Having fewer than six spots, even if they meet size criteria, does not fulfill this particular NIH diagnostic criterion for NF1, though other features should still be assessed. 2
When to Escalate Concern Beyond Spot Count
Even with fewer than six spots, immediate genetics referral is warranted if the child has: 2
- Developmental delays or hypotonia (suggests constitutional mismatch repair deficiency syndrome or other genetic conditions)
- Dysmorphic facial features, congenital heart defects, or short stature (suggests RASopathies like Noonan or Costello syndrome) 2
- Childhood leukemia, brain tumors, or GI malignancies (suggests constitutional mismatch repair deficiency syndrome with extremely high cancer risk) 2
Complete Documentation Requirements
When evaluating café au lait spots, you must: 2
- Document the exact number and measure the diameter of each spot (not just note their presence)
- Examine axillary and inguinal regions for freckling (Crowe's sign, highly specific for NF1)
- Look for cutaneous or subcutaneous neurofibromas
- Perform slit-lamp examination for Lisch nodules (iris hamartomas)
Common Pitfall to Avoid
Do not dismiss multiple café au lait spots in a child simply because they lack other obvious features of NF1 at initial presentation. 2 NF1 manifestations evolve over time, and early identification allows for critical surveillance that reduces morbidity and mortality from complications including malignant peripheral nerve sheath tumors (15.8% cumulative risk by age 85) and cardiovascular disease. 2